As the coiled tubing technology is developed continuously, the demand for applying the coiled tubing technology in deep well and extra-deep well operations becomes more and more urgent and frequent. Halliburton has utilized variable outer diameter coiled tubing technique to improve the maximum vertical depth of operation to 10,000 m or above; Schlumberger and other companies have many success cases of coiled tubing operation in deep wells and extra-deep wells in depth greater than 6,000 m. However, the reels used by those companies for deep-well large-diameter coiled tubing operation are ultra-large, ultra-wide, and ultra-high. For example, the outer diameter of a reel for coiled tubing in 2″ outer diameter with 7,600 m capacity is as large as 4.5 m. Such coiled tubing reels can't be transported successfully under the limited road conditions in China.
In addition, compared with small reels or large reels without limited structural dimensions, extra-deep well coiled tubing reels involve many problems in terms of driving, owing to the high strength grade, large pipe diameter, great wall thickness, great length, heavy weight, and limited structural dimensions of coiled tubing wound on the coiled tubing reels; specifically, the existing reels for coiled tubing operation usually use two driving modes, wherein, one driving mode is a directly driving structure using a motor reducer, but the torque transferred in this driving mode is low and can't meet the winding requirement; the other driving mode is to use chain transmission structure with a motor reducer, but the structural dimensions are large, the transmission is not steady, and the chain may be worn easily.
Therefore, there is a demand for a coiled tubing reel that can increase the coiled tubing winding capacity, provides high transmission torque, and operates smoothly and steadily at a low speed, while meeting the requirement for transportation dimensions.